NOTE. Bank note, manufacture of. A block of thick plate steel is softened on the upper side ; the device is engraved on this softened surface ; the block is hardened by a careful process after the engraving ; the device is transferred from the hardened block to the convex sur face of a small soft steel roller, by in tense pressure ; the roller is hardened, and the device is transferred from it to any number of softened steel plates ; these plates are hardened after the trans fer, and are then in a state to be printed from. By this beautiful train of opera tions, one originally engraved block is made to suffice for an almost endless number of engravings. The mode in which the writing, the emblems, and the ornaments are combined in a bank-note, is so planned as to render forgery diffi cult. The numbering is a remarkable process, as now performed. Four wheels, each divided by ten notches, leaving a face between each pair, engraved with consecutive numbers from 1 to 0, are placed upon a shaft : a portion of their breadth being turned down about one half of their depth, having a boss or collar between every two. Upon these bosses, and filling up the spaces, rest latches ; and over each wheel is a pall, the width of the first being equal to that of the unit wheel, and the breadth of the others equalling that of the wheel and latch. The palls are driven by a crank ; by each revolution of which the first wheel is moved through a space equal to one tenth of its entire circumference, bring ing regularly forward the numbers from 1 to 0. When the figure 0 is reached, the
latch of the second wheel is depressed, and the wheel moves forward one divi sion, making the tens. The same process is repeated with regard to the other wheels, and thus any amount of num bers can be registered, by simply increas ing the number of wheels in proportion. Machines of this kind are extensively adopted in the Bank of England ; with, of coarse, an inking apparatus to apply to the types. A patent was taken out in 1844 for a mode of printing bank-notes intended to obviate the liability to forgery. The sur face is covered with two designs, one geometrically regular, and the other very irregular ; the two designs are engraved on different plates, and are printed with different inks, the one with visible and the other with invisible ink. Both of the inks are delible, or removable by chemical means ; and the usual engrav ing of a hank note is printed on paper so prepared. The rationale of the sugges tion is this—that whatever means a for ger might take to alter, by chemical agency, the letters or figures, or to trans fer them by lithographic or :mastic pro cesses, the state of the paper would be tray him ; for he would remove some parts of the design in the one case, and fail to transfer in the other.